[R] Need help on parsing dates

[Jean Eid]

 ?as.POSIXlt

On Tue, 24 Feb 2004, Ajay Shah wrote:

> I know this:
>
>   > library(date)
>   > x="1979-04-04"
>   > try=as.date(x, "ymd")
>   > print(try)
>   [1] 4Apr79
>
> and that `x' here has to be a string, e.g.:
>
>   > x=1979-04-04
>   > print(x)
>   [1] 1971
>
> I'm stuck in reading from a file. I say:
>
>   > A <- read.table(file="try")
>   > print(A)
>              V1          V2
>   1  1979-04-04 -1.04712042
>   2  1979-04-06  0.54538055
>   3  1979-04-09  0.09663392
>   4  1979-04-11  0.57119871
>   5  1979-04-12  0.73594112
>   6  1979-04-17 -1.54422087
>   7  1979-04-18 -0.20595691
>   8  1979-04-19  0.12700429
>   9  1979-04-20  0.42016807
>   10 1979-04-23 -1.46838241
>
> I am confused - is V1 a number or a string? Looking at it, it must be
> a string. But yet:
>
>   > library(date)
>   > try=as.date(A$V1, "ymd")
>   Error in as.date(A$V1, "ymd") : Cannot coerce to date format
>
> In short, how do I parse in dates of the format yyyy-mm-dd (the ISO
> 8601 format) or the yyyymmdd format.
>
> And if I may ask the next step: How do I tell R that I have a file
> full of data all of which is time-series data, where V1 is the
> datetime vector, and all the other columns are time-series, to do
> things like ARMA models and ts plots with?
>
> --
> Ajay Shah                                                   Consultant
> ajayshah at mayin.org                      Department of Economic Affairs
> http://www.mayin.org/ajayshah           Ministry of Finance, New Delhi
>
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